Note that the following discussion refers to a number of publications by author(s) and year of publication. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Surface modification of medical implants is frequently desired to increase cell adhesion and tissue integration into the implant. Increasing cell adhesion is of particular interest with polytetrafluoroethylene (ePTFE) prostheses but is also of interest in implants of other materials, such as titanium which is frequently used in orthopedic applications. (See for example Bellon et al. Similarity in behavior of polytetrafluoroethylene (ePTFE) prostheses implanted into different interfaces. J Biomed Mater Res 31 (1996) 1-9; Bagno and Di Bello, Surface treatments and roughness properties of Ti-based biomaterials. J Mater Sci Mater Med 15 (2004) 935-49; and Goto et al. The initial attachment and subsequent behavior of osteoblastic cells and oral epithelial cells on titanium. Biomed Mater Eng 14 (2004) 537-44).
One approach to increasing cell adhesion is the use of bioactive cell adhesion peptides motifs found in extracellular matrix molecules such as collagens, fibronectin, and laminin, among others. As an example, P-15, a collagen-derived peptide, increases cell attachment and modulates a number of gene products, and has been incorporated into a commercially-available dental implant. (See for example Bhatnagar et al. Design of biomimetic habitats for tissue engineering with P-15, a synthetic peptide analogue of collagen., Tissue Eng 5 (1999) 53-65; Carinci et al. P-15 cell-binding domain derived from collagen: analysis of MG63 osteoblastic-cell response by means of a microarray technology. J Periodontol 75 (2004) 66-83; and Lucidarme, et al. Angiogenesis model for ultrasound contrast research: exploratory study, Acad Radiol 11 (2004) 4-12).
Other peptides with cell binding motifs that have been investigated for use on implants include those based on RGD, YIGSR (SEQ ID NO:1) and IKVAV (SEQ ID NO:2) motifs derived from laminin. Heparin-binding peptides including those from laminin can also directly promote cell adhesion and may also be similarly used. (See for example Shin et al. Biomimetic materials for tissue engineering. Biomaterials 24 (2003) 4353-64; Skubitz et al. Synthetic peptides from the carboxy-terminal globular domain of the A chain of laminin: their ability to promote cell adhesion and neurite outgrowth, and interact with heparin and the beta 1 integrin subunit. J Cell Biol 115 (1991) 1137-48; Yokoyama et al. Cyclic peptides from the loop region of the laminin alpha 4 chain LG4 module show enhanced biological activity over linear peptides. Biochemistry 43 (2004) 13590-7; and Yoshida et al. Identification of a heparin binding site and the biological activities of the laminin alpha1 chain carboxy-terminal globular domain. J Cell Physiol 179 (1999) 18-28).
Also known are constructs called heterogeneous mimetic peptide surfaces (MPS) containing both RGD (cell-binding) and FHRRIKA (SEQ ID NO:18) (putative heparin-binding) sequences, which are reported to enhance cell attachment and differentiation. (See for example Healy et al. Designing biomaterials to direct biological responses. Ann N Y Acad Sci 875 (1999) 24-35).
Laminins are large glycoproteins (molecular mass≈900 kDa) found in basement membranes where they are major components. (See for example Colognato and Yurchenco. Form and function: the laminin family of heterotrimers. Dev Dyn 218 (2000) 213-34). Laminin-1 consists of three chains designated a1 (400 kDa), b1 (210 kDa) and c1 (200 kDa), which are arranged in a cross-shaped structure, and contribute to cell differentiation, cell shape and movement, maintenance of tissue phenotypes, and promotion of tissue survival. Laminin binds heparin as do laminin-derived peptides such as KEGYKVRLDLNITLEFRTTSK (SEQ ID NO:3) and KATPMLKMRTSFHGCIK (SEQ ID NO:4); IKLLI (SEQ ID NO:5), and KDFLSIELVRGRVK (SEQ ID NO:6). (See for example Edgar and Thoenen. The heparin-binding domain of laminin is responsible for its effects on neurite outgrowth and neuronal survival. Embo J 3 (1984) 1463-8; Skubitz, et al. Synthetic peptides from the carboxy-terminal globular domain of the A chain of laminin: their ability to promote cell adhesion and neurite outgrowth, and interact with heparin and the beta 1 integrin subunit. J Cell Biol 115 (1991) 1137-48; Tashiro et al. An IKLLI-containing peptide derived from the laminin alpha1 chain mediating heparin-binding, cell adhesion, neurite outgrowth and proliferation, represents a binding site for integrin alpha3beta1 and heparan sulphate proteoglycan. Biochem J 340 (Pt 1) (1999) 119-26; Yoshida et al. Identification of a heparin binding site and the biological activities of the laminin alpha1 chain carboxy-terminal globular domain. J Cell Physiol 179 (1999) 18-28).
Those peptides also affect cell adhesion. Laminin also contains numerous other cell-adhesion sites in its α, β, and γ chains including RGD LGTIPG (SEQ ID NO:7), YIGSR (SEQ ID NO:1), RYVVLPR (SEQ ID NO:8), PDSGR (SEQ ID NO:9), YFQRYLI (SEQ ID NO:10), LRE, IKLLI (SEQ ID NO:11), RNIAEIIKDI (SEQ ID NO:12), SIYITRF (SEQ ID NO:13), IARQRN (SEQ ID NO:14), LQVQLSIR (SEQ ID NO:15), IKVAV (SEQ ID NO:2), and several others in the globular domain (GD) of the α chain. At the cell surface, RGD and KQNCLSSRASFRGCVRNLRLSR (SEQ ID NO:17) (the GD-6 peptide) bind to integrins; YIGSR (SEQ ID NO:1) and LGTIPG (SEQ ID NO:7) bind to a 67 kDa protein; and IKVAV (SEQ ID NO:2) to a 110 kDa protein.
The central role of laminins in cell attachment has, in part, lead to studies using laminin to improve cell attachment to implants, including vascular grafts, neural implants, and dental implants. (See for example J. W. Dean, 3rd et al. Fibronectin and laminin enhance gingival cell attachment to dental implant surfaces in vitro. Int J Oral Maxillofac Implants 10 (1995) 721-8; Healy et al. Designing biomaterials to direct biological responses. Ann N Y Acad Sci 875 (1999) 24-35; Huber et al. Modification of glassy carbon surfaces with synthetic laminin-derived peptides for nerve cell attachment and neurite growth. J Biomed Mater Res 41 (1998) 278-88; Kidd et al. Stimulated endothelial cell adhesion and angiogenesis with laminin-5 modification of expanded polytetrafluoroethylene. Tissue Eng 11 (2005) 1379-91; Kidd and Williams. Laminin-5-enriched extracellular matrix accelerates angiogenesis and neovascularization in association with ePTFE. J Biomed Mater Res A 69 (2004) 294-304; Massia et al. In vitro assessment of bioactive coatings for neural implant applications. J Biomed Mater Res A 68 (2004) 177-86; Tamura et al. Coating of titanium alloy with soluble laminin-5 promotes cell attachment and hemidesmosome assembly in gingival epithelial cells: potential application to dental implants. J Periodontal Res 32 (1997) 287-94).
While recombinant laminins have been made, a synthetic peptide based on laminin may provide significant advantages for use on medical devices. (See for example Kortesmaa et al. Recombinant laminin-8 (alpha(4)beta(1)gamma(1)). Production, purification, and interactions with integrins. J Biol Chem 275 (2000) 14853-9; Mathus and Yurchenco. Analysis of laminin structure and function with recombinant glycoprotein expressed in insect cells. Methods Mol Biol 139 (2000) 27-37; Sung et al. Localization of heparin binding activity in recombinant laminin G domain. Eur J Biochem 250 (1997) 138-43; Yurchenco et al. Recombinant laminin G domain mediates myoblast adhesion and heparin binding. J Biol Chem 268 (1993) 8356-65).
IKVAV (SEQ ID NO:2) promotes cell adhesion and differentiation of several different cell types. With endothelial cells for example, IKVAV (SEQ ID NO:2) induces tube formation, aortic spouting, angiogenesis, and mediates revascularization of ischemic tissue. (See for example Huber et al. Modification of glassy carbon surfaces with synthetic laminin-derived peptides for nerve cell attachment and neurite growth. J Biomed Mater Res 41 (1998) 278-88., Grant et al. Interaction of endothelial cells with a laminin A chain peptide (SIKVAV) in vitro and induction of angiogenic behavior in vivo. J Cell Physiol 153 (1992) 614-25; Grant and Zukowska. Revascularization of ischemic tissues with SIKVAV and neuropeptide Y (NPY), Adv Exp Med Biol 476 (2000) 139-54; Malindary et al. Ponce, Identification of laminin alpha1 and beta1 chain peptides active for endothelial cell adhesion, tube formation, and aortic sprouting, Faseb J 13 (1999) 53-62). With nerve cells, IKVAV (SEQ ID NO:2) also mediates cell attachment and growth and has been used in the construction of experimental nerve guides. (See for example Massia et al. In vitro assessment of bioactive coatings for neural implant applications. J Biomed Mater Res A 68 (2004) 177-86; D. Shaw and M. S. Shoichet. Toward spinal cord injury repair strategies: peptide surface modification of expanded poly(tetrafluoroethylene) fibers for guided neurite outgrowth in vitro. J Craniofac Surg 14 (2003) 308-16; Tong and Shoicliet. Enhancing the neuronal interaction on fluoropolymer surfaces with mixed peptides or spacer group linkers. Biomaterials 22 (2001) 1029-34).
Laminin-derived constructs described as peptide amphiphiles are known, which constructs incorporate a hydrophobic component. Linear constructs are described in U.S. Patent Application 2005/0214257, published Sep. 29, 2005, and non-linear constructs are described in U.S. Patent Application 2005/0208589, published Sep. 22, 2005. However, none of these constructs include a heparin-binding component. Additionally, these constructs are described primarily as useful for stem cell regulation, enhancing epitope presentation and similar indications.
There is thus a need for cost-effective synthetic peptide constructs that promote cellular attachment, and are useful for coating medical devices and as soluble biologics, and as pharmaceutical agents for treating a variety of conditions.